#include <bits/stdc++.h>
#define ll long long
using namespace std;

const int dx[] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
const int dy[] = {0, 1, 2, 2, 1, -1, -2, -2, -1};

int bx, by, mx, my;
ll f[25][25] = {1};
bool vis[25][25];

int main()
{
  	cin >> bx >> by >> mx >> my;
  	for(int i = 0; i < 9; i++){
  		int tx=mx+dx[i],ty=my+dy[i];
		if(0<=tx&&tx<=bx&&0<=ty&&ty<=by) vis[tx][ty]=1;
	  }
    for(int i = 0; i <= bx; i++){
    	for(int j = 0; j <= by; j++){
    		if(!vis[i][j]){
    			if(i > 0) f[i][j] += f[i-1][j];
    			if(j > 0) f[i][j] += f[i][j-1];
			}
		}
	}
	cout << f[bx][by] << endl;
  return 0;
}	